The present invention relates to a circuit arrangement for tuning into one of a number of radioelectric signals receivable on a signal receiver, in particular, a radio receiver, and comprises a controllable oscillator the frequency of which is determined by a control loop depending on a digital number, N, coming from a processing unit, in turn, dependent on coded input data; the said loop in particular comprises frequency dividing means for obtaining from the controllable oscillator to a first signal dependent at least on the said number N and means for comparing the said first signal with a second frequency reference signal so as to obtain a third signal suitable for required tuning.
Circuit arrangements of this type are known to be used on radio receivers and provide for considerable improvement of receiver characteristics as compared with known non-frequency-synthesizer types especially as regards tuning accuracy and stability. These characteristics are particularly important when radio receivers are tuned for frequency modulation reception on the 87-108 MHz frequency band on which a large number of radioelectric signals can be received. Moreover, in these circuit arrangements have been provided circuits which, during the tuning, block the output signal to avoid disturbance signals to the loudspeaker, but they have the disadvantage of being activated in the presence of a generic change of tuning, and do not operate as a function of the particular type of tuning chosen by the user.